Sketch is a nice minimal portfolio theme by WordPress.com, which is available for free on their website. The theme comes with a integrated portfolio function, which allows you to integrate large images with a size up to 1272px. You can set your favorite image format by the in-build image customizer. Following formats are available: landscape (4:3) portrait (3:4) square (1:1) Also good, custom shortcodes can be added fast and easy by using the [portfolio] tag. Another great feature is the in-build social link function, which display the social icon, if you set a link to a social network, like facebook, Google+...